Heat Resistant Toughened Themoplastic Composition for Injection Molding

ABSTRACT

Injection molded parts with a small dimension that exhibit high heat resistance are described. Thermoplastic compositions that can be utilized to form the injection molded parts are described. The thermoplastic composition includes a polyarylene sulfide and a crosslinked impact modifier. The thermoplastic composition can also include siloxane polymers, thermoplastic elastomers, or other additives that can further improve the characteristics of the injection molded parts.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims filing benefit of U.S. Provisional patentApplication Ser. No. 61/870,356 having a filing date of Aug. 27, 2013,which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

Injection molded parts with small dimensional tolerances are in highdemand in various industries (e.g., electronic, automotive, etc.). Inthese applications, the thermoplastic composition must have good flowproperties so that it can quickly and uniformly fill the small spaces ofthe mold cavity. In addition, the formed part should exhibit desiredqualities such as flexibility while withstanding expected stressesduring use.

Injection molded polymer blends that exhibit flexibility in addition tohigh strength and resistance properties are of significant commercialinterest. Such blends have been formed in the past by uniformly mixingan elastic component with a thermoplastic polyolefin such that theelastomer is intimately and uniformly dispersed as a discrete orco-continuous phase within a continuous phase of the polyolefin.Vulcanization of the composite crosslinks the components and providesimproved temperature and chemical resistance to the composition. Whenvulcanization is carried out during combination of the various polymericcomponents it is termed dynamic vulcanization. Unfortunately, injectionmolded products of small dimensions formed from dynamically vulcanizedpolyolefin blends fail to provide the desired strength and resistanceproperties in many applications.

Polyarylene sulfides are high-performance polymers that may withstandhigh thermal, chemical, and mechanical stresses and are beneficiallyutilized in a wide variety of applications. Polyarylene sulfides haveoften been blended with other polymers to improve characteristics of theproduct composition. For example, elastomeric impact modifiers have beenfound beneficial for improvement of the physical properties of athermoplastic composition. Compositions including blends of polyarylenesulfides with impact modifying polymers have been considered for highperformance, high temperature applications.

Unfortunately, elastomeric polymers generally considered useful forimpact modification are not compatible with polyarylene sulfides andphase separation has been a problem in forming compositions of the two.This can be particularly problematic when forming products having smalldimensions. Attempts have been made to improve the compositionformation, for instance through the utilization of compatibilizers.However, even upon such modifications, compositions includingpolyarylene sulfides in combination with impact modifying polymers stillfail to provide product performance as desired, particularly in smalldimension injection molded parts that require both high heat resistanceand high impact resistance.

What are needed in the art are thermoplastic compositions that can beinjection molded to form small dimension products that exhibit highstrength characteristics as well as resistance to degradation, even inextreme temperature environments.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present invention, an injectionmolded part is disclosed. The part has a thickness of about 100millimeters or less and is formed from a thermoplastic composition thatcomprises a polyarylene sulfide and a crosslinked impact modifier. Thethermoplastic composition exhibits high toughness and good flexibilityas well as excellent heat resistance. For instance, the injection moldedpart can exhibit a notched Charpy impact strength of about 3 kJ/m² orgreater as measured according to ISO Test No. 179-1 at a temperature of23° C. and the injection molded part can exhibit about 60% or morestrength retention following heat aging at 165° for 1000 hours.Injection molded parts that can be formed from the thermoplasticcomposition can include fasteners such as clips, cable ties, cable tiesaddles, and the like. The injection molded parts can be particularlywell suited for use in extreme temperatures and/or in applications inwhich temperatures may vary over a wide margin.

Also disclosed is a method for forming an injection molded part from thethermoplastic composition. A method can include injecting athermoplastic composition into a mold cavity. More specifically, thethermoplastic composition can include a polyarylene sulfide and acrosslinked impact modifier. The thermoplastic composition can have amelt viscosity of about 3 kilopoise or less as determined by a capillaryrheometer at a temperature of 310° C. and shear rate of 1200 seconds⁻¹.The method can also include ejecting the molded part from the cavity,the molded part having a thickness of about 100 millimeters or less.

BRIEF DESCRIPTION OF THE FIGURES

The present disclosure may be better understood with reference to thefollowing figures:

FIG. 1 is a representation of a cable tie that may be formed from thethermoplastic composition.

FIG. 2 is a representation of a cable tie following closure of the tie.

FIG. 3A, FIG. 3B and FIG. 3C illustrate examples of other products thatcan be formed from the thermoplastic composition.

FIG. 4 is a schematic representation of a process for forming thethermoplastic composition as disclosed herein.

FIG. 5 is a cross-sectional view of one embodiment of an injection moldapparatus that may be employed in the present invention.

FIG. 6 graphically illustrates the loop strength retention of aninjection molded cable tie during heat aging.

DETAILED DESCRIPTION

It is to be understood by one of ordinary skill in the art that thepresent discussion is a description of exemplary embodiments only, andis not intended as limiting the broader aspects of the presentdisclosure.

The present disclosure is generally directed to injection molded partswith a small dimension that exhibit excellent physical characteristics.Also disclosed are thermoplastic compositions that can be utilized toform the injection molded parts. Beneficially, the small dimensioninjection molded parts can maintain good physical characteristics evenwhen utilized in extreme temperature applications such as hightemperatures as may be encountered in automotive applications and lowtemperatures as may be encountered in piping applications. Thethermoplastic composition can also maintain good physicalcharacteristics under conditions in which the materials are subjected toextreme temperature fluctuations.

Generally speaking, the present invention is directed to an injectionmolded part that has a relatively small thickness and exhibitsflexibility and high strength characteristics so that it can be readilyemployed in a wide variety of applications. For example, the part may bein the form of a substrate having a thickness of about 100 millimetersor less, in some embodiments about 50 millimeters or less, in someembodiments from about 100 micrometers to about 10 millimeters, and insome embodiments, from about 200 micrometers to about 1 millimeter. Thepart can have a length and/or width dimension that is larger than thethickness. For instance, the part can have a length dimension that isabout 5 centimeters or greater, in some embodiments about 10 centimetersor greater, in some embodiments from about 5 centimeters to about 200centimeters, and in some embodiments from about 10 centimeters to about100 centimeters. In some embodiments the part can have an aspect ratio(length/width) that is about 1 or greater. For instance the part canhave an aspect ratio that is about 5 or greater, in some embodiments theaspect ratio can be about 10 or greater, for instance from about 5 toabout 500, or from about 10 to about 300.

Examples of molded parts include, for instance, fasteners as may bebeneficially utilized in a variety of applications. Exemplary fastenerscan include cable ties, clips, bands, harnesses, tapes, cable tiesaddles, and so forth. FIG. 1 illustrates a cable tie 50 as may beformed. As can be seen the cable tie 50 includes a tape section 51. Thetape section 51 can include a series of teeth that slope in onedirection. The head 52 of the cable tie defines a slot 53. The slot 53can be sized such that distal end 54 of the tape section 51 can fit intothe slot 53. In the illustrated embodiment, the end 54 is tapered, whichcan facilitate feeding the end 54 into the slot 53, but this is not arequirement of the cable tie. The slot 53 of the head 52 also includes apawl that can irreversibly ride up the teeth of the tape section 52 whenthe tape section 52 is fed through the slot 53. The pawl engages thebackside of the teeth to stop movement of the tape in the reversaldirection and thus preventing opening of the cable tie. FIG. 2illustrates the cable tie 50 following closure. As can be seen the tapesection 51 is fed through the slot 53 of the head 52 to irreversiblyclose. The cable tie 50 can be conveniently utilized to fastenstructures (e.g., pipes, wires, cables, ropes, etc.) to one another.

Of course, a large variety of products are encompassed in the presentdisclosure and the disclosure is in no way limited to cable ties asillustrated in FIG. 2. Modified cable ties are also encompassed herein.For example, FIG. 3A illustrates a fir tree mount cable tie as may beformed from the thermoplastic composition. A fir tree mount cable tie isuseful in a variety of applications, and particularly in blind assemblyapplications as the fir tree 54 can be located within the receiving disc55 merely by feel if necessary. The staggered design of the fir tree 54provides low insertion forces and high extraction forces so as toprevent release following utilization of the fir tree mount cable tie.

Other applications of the thermoplastic composition can include clampssuch as the hose clamp illustrated in FIG. 3B and the tube clipillustrated in FIG. 3C. Products formed from the thermoplasticcomposition such as the clamps and clips illustrated herein can providesecure attachment under adverse conditions, and particularly under hightemperature applications as may be found in, e.g., automobile engineapplications.

To achieve the desired properties of the molded parts, the parts can beformed from a melt processed thermoplastic composition that includes apolyarylene sulfide. More specifically, the thermoplastic compositioncan be formed by combining a polyarylene sulfide with an impact modifierto form a mixture and subjecting the mixture to dynamic vulcanization.During formation of the thermoplastic composition, the polyarylenesulfide can be combined with the impact modifier and this mixture can besubjected to shear conditions such that the impact modifier becomes welldistributed throughout the polyarylene sulfide. Following formation ofthe mixture, a polyfunctional crosslinking agent can be added. Thepolyfunctional crosslinking agent can react with the components of themixture to form crosslinks in the composition, for instance within andbetween the polymer chains of the impact modifier.

Without being bound to any particular theory, it is believed that byadding the polyfunctional crosslinking agent to the thermoplasticcomposition following distribution of the impact modifier throughout thepolyarylene sulfide, interaction between the polyarylene sulfide, theimpact modifier, and the crosslinking agent within the melt processingunit can be improved, leading to improved distribution of thecrosslinked impact modifier throughout the composition. The improveddistribution of the crosslinked impact modifier throughout thecomposition can improve the strength and flexibility characteristics ofthe composition, e.g., the ability of the composition to maintainstrength under deformation, as well as provide a composition with goodprocessibility that can be utilized to form a product that can exhibitexcellent resistance to degradation under a variety of conditions.

According to one embodiment, a formation process can includefunctionalization of the polyarylene sulfide. This embodiment canprovide additional sites for bonding between the impact modifier and thepolyarylene sulfide, which can further improve distribution of theimpact modifier throughout the polyarylene sulfide and further preventphase separation. Moreover, functionalization of the polyarylene sulfidecan include scission of the polyarylene sulfide chain, which candecrease the melt viscosity of the composition and improveprocessibility. This can also provide a composition that is a lowhalogen composition, e.g., low chlorine composition that exhibitsexcellent physical characteristics and high resistance to degradation.

To provide further improvements to the thermoplastic composition, thecomposition can be formed to include other additives. For instance, thecomposition can include one or more additional polymers such as asilicone polymer or a thermoplastic elastomer. In those embodiments inwhich the thermoplastic composition includes another polymer inconjunction with the other components, for instance a silicone polymer,it may also prove beneficial to include a coupling agent that canimprove bonding between the additional polymer and the polyarylenesulfide. The composition can also include traditional additives such asfillers, lubricants, colorants, etc. according to standard practice.

The high strength, flexibility, and heat resistant characteristics ofthe thermoplastic composition can be evident by examination of thetensile, flexural, and/or impact properties of the materials. Forexample, the thermoplastic composition (or the injection molded partformed from the composition) can have a notched Charpy impact strengthof greater than about 3 kJ/m², greater than about 3.5 kJ/m², greaterthan about 5 kJ/m², greater than about 10 kJ/m², greater than about 15kJ/m², greater than about 30 kJ/m², greater than about 33 kJ/m², greaterthan about 40 kJ/m², greater than about 45 kJ/m², or greater than about50 kJ/m² as determined according to ISO Test No. 179-1 (technicallyequivalent to ASTM D256, Method B) at 23° C. The unnotched Charpysamples do not break under testing conditions of ISO Test No. 180 at 23°C. (technically equivalent to ASTM D256).

Beneficially, the thermoplastic composition can maintain good physicalcharacteristics even at extreme temperatures, including both high andlow temperatures. For instance, the thermoplastic composition (or theinjection molded part formed from the composition) can have a notchedCharpy impact strength of greater than about 8 kJ/m², greater than about9 kJ/m², greater than about 10 kJ/m², greater than about 14 kJ/m²,greater than about 15 kJ/m², greater than about 18 kJ/m², or greaterthan about 20 kJ/m² as determined according to ISO Test No. 179-1 at−30° C.; and can have a notched Charpy impact strength of greater thanabout 8 kJ/m², greater than about 9 kJ/m², greater than about 10 kJ/m²,greater than about 11 kJ/m², greater than about 12 kJ/m², or greaterthan about 15 kJ/m² as determined according to ISO Test No. 179-1 at−40° C.

Moreover, the effect of temperature change on the thermoplasticcomposition can be surprisingly small. For instance, the ratio of thenotched Charpy impact strength as determined according to ISO Test No.179-1 at 23° C. to that at −30° C. can be greater than about 3.5,greater than about 3.6, or greater than about 3.7. Thus, and asdescribed in more detail in the example section below, as thetemperature increases the impact strength of the thermoplasticcomposition also increases, as expected, but the rate of increase of theimpact strength is very high, particularly as compared to a compositionthat does not include the dynamically crosslinked impact modifier.Accordingly, the thermoplastic composition can exhibit excellentstrength characteristics at a wide range of temperatures.

The thermoplastic composition can also exhibit excellent heat resistanceand thus can be utilized continuously at high temperature, for instanceat a continuous use temperature of up to about 150° C., about 160° C.,or about 165° C. without loss of tensile strength. For instance, the aninjection molded part formed of the thermoplastic composition canexhibit about 60% or more strength retention, about 65% or more strengthretention, or about 70% or more strength retention following heat agingat 165° C. for 1000 hours. In one embodiment, the thermoplasticcomposition can maintain greater than about 95%, for instance about 100%of the original tensile strength after 1000 hours of heat aging at 135°C. and can maintain greater than about 95%, for instance about 100% ofthe original tensile elongation at yield after 1000 hours heat aging at135° C.

The thermoplastic composition can also exhibit flame retardantcharacteristics. For instance, the composition can meet the V-0flammability standard at a thickness of 0.2 millimeters. The flameretarding efficacy may be determined according to the UL 94 VerticalBurn Test procedure of the “Test for Flammability of Plastic Materialsfor Parts in Devices and Appliances”, 5th Edition, Oct. 29, 1996. Theratings according to the UL 94 test are listed in the following table:

Rating Afterflame Time (s) Burning Drips Burn to Clamp V-0 <10 No No V-1<30 No No V-2 <30 Yes No Fail <30 Yes Fail >30 No

The “afterflame time” is an average value determined by dividing thetotal afterflame time (an aggregate value of all samples tested) by thenumber of samples. The total afterflame time is the sum of the time (inseconds) that all the samples remained ignited after two separateapplications of a flame as described in the UL-94 VTM test. Shorter timeperiods indicate better flame resistance, i.e., the flame went outfaster. For a V-0 rating, the total afterflame time for five (5)samples, each having two applications of flame, must not exceed 50seconds. Using the flame retardant of the present invention, articlesmay achieve at least a V-1 rating, and typically a V-0 rating, forspecimens having a thickness of 0.2 millimeters.

The thermoplastic composition may possess a relatively low meltviscosity, which allows it to readily flow into the mold cavity duringproduction of the part. For instance, the composition may have a meltviscosity of about 3 kilopoise or less, in some embodiments about 2kilopoise or less, and in some embodiments, from about 0.1 to about 1kilopoise, as determined by a capillary rheometer at a temperature of310° C. and shear rate of 1200 seconds⁻¹. Among other things, theseviscosity properties can allow the composition to be readily injectionmolded into parts having very small dimensions without producingexcessive amounts of flash. Moreover, the thermoplastic composition canexhibit improved melt stability over time as compared to thermoplasticcompositions that do not include crosslinked impact modifiers.Thermoplastic compositions that do not include a crosslinked impactmodifier tend to exhibit an increase in melt viscosity over time, and incontrast, disclosed compositions can maintain or even decrease in meltviscosity over time.

The thermoplastic composition can have a complex viscosity as determinedat low shear (0.1 radians per second (rad/s)) and 310° C. of greaterthan about 10 kPa·sec, greater than about 25 kPa·sec, greater than about40 kPa·sec, greater than about 50 kPa·sec, greater than about 75kPa·sec, greater than about 200 kPa·sec, greater than about 250 kPa·sec,greater than about 300 kPa·sec, greater than about 350 kPa·sec, greaterthan about 400 kPa·sec, or greater than about 450 kPa·sec. Higher valuefor complex viscosity at low shear is indicative of the crosslinkedstructure of the composition and the higher melt strength of thethermoplastic composition. In addition, the thermoplastic compositioncan exhibit high shear sensitivity, which indicates excellentcharacteristics for use in formation processes such as blow molding andextrusion processing.

The thermoplastic composition (and the part formed from the composition)can exhibit very good tensile characteristics. For example, thethermoplastic composition can have a tensile elongation at yield ofgreater than about 4.5%, greater than about 6%, greater than about 7%,greater than about 10%, greater than about 25%, greater than about 35%,greater than about 50%, greater than about 70%, greater than about 75%,greater than about 80%, or greater than about 90%. Similarly, thetensile elongation at break can be quite high, for instance greater thanabout 10%, greater than about 25%, greater than about 35%, greater thanabout 50%, greater than about 70%, greater than about 75%, greater thanabout 80%, or greater than about 90%. The strain at break can be greaterthan about 5%, greater than about 15%, greater than about 20%, orgreater than about 25%. For instance the strain at break can be about90%. The yield strain can likewise be high, for instance greater thanabout 5%, greater than about 15%, greater than about 20%, or greaterthan about 25%. The yield stress can be, for example, greater than about50% or greater than about 53%. The thermoplastic composition may have atensile strength at break of greater than about 30 MPa, greater thanabout 35 MPa, greater than about 40 MPa, greater than about 45 MPa, orgreater than about 70 MPa.

In addition, the thermoplastic composition can have a relatively lowtensile modulus. For instance, the thermoplastic composition can have atensile modulus less than about 3000 MPa, less than about 2300 MPa, lessthan about 2000 MPa, less than about 1500 MPa, or less than about 1100MPa as determined according to ISO Test No. 527 at a temperature of 23°C. and a test speed of 5 mm/min.

The thermoplastic composition can exhibit good characteristics afterannealing as well. For instance, following annealing at a temperature ofabout 230° C. for a period of time of about 2 hours, the tensile modulusof the composition can be less than about 2500 MPa, less than about 2300MPa, or less than about 2250 MPa. The tensile strength at break afterannealing can be greater than about 50 MPa, or greater than about 55MPa, as measured according to ISO Test No. 527 at a temperature of 23°C. and a test speed of 5 mm/min.

Tensile characteristics can be determined according to ISO Test No. 527at a temperature of 23° C. and a test speed of 5 mm/min or 50 mm/min(technically equivalent to ASTM D623 at 23° C.).

The flexural characteristics of the composition can be determinedaccording to ISO Test No. 178 (technically equivalent to ASTM D790 at atemperature of 23° C. and a testing speed of 2 mm/min. For example, theflexural modulus of the composition can be about 2500 MPa or less, about2300 MPa or less, about 2000 MPa or less, about 1800 MPa or less, orabout 1500 MPa or less. The thermoplastic composition may have aflexural strength at break of about 30 MPa or greater, about 35 MPa orgreater, about 40 MPa or greater, about 45 MPa or greater, or about 70MPa or greater.

The deflection temperature under load of the thermoplastic compositioncan be relatively high. For example, the deflection temperature underload of the thermoplastic composition can be greater than about 80° C.,greater than about 90° C., greater than about 100° C., or greater thanabout 105° C., as determined according to ISO Test No. 75-2 (technicallyequivalent to ASTM D790) at 1.8 MPa.

The Vicat softening point can be greater than about 200° C. or greaterthan about 250° C., for instance about 270° C. as determined accordingto the Vicat A test when a load of 10 N is used at a heating rate of 50K/hr. For the Vicat B test, when a load of 50 N is used at a heatingrate of 50 K/hr, the Vicat softening point can be greater than about100° C., greater than about 150° C. greater than about 175° C., orgreater than about 190° C., for instance about 200° C. The Vicatsoftening point can be determined according to ISO Test No. 306(technically equivalent to ASTM D1525).

The thermoplastic composition can also exhibit excellent stabilityduring long term exposure to harsh environmental conditions. Forinstance, under long term exposure to an acidic environment, thethermoplastic composition can exhibit little loss in strengthcharacteristics. For instance, following 500 hours exposure to a strongacid (e.g., a solution of about 5% or more strong acid such as sulfuricacid, hydrochloric acid, nitric acid, perchloric acid, etc.), thethermoplastic composition can exhibit a loss in Charpy notched impactstrength of less than about 17%, or less than about 16% followingexposure of about 500 hours to a strong acid solution at a temperatureof about 40° C., and can exhibit a loss in Charpy notched impactstrength of less than about 25%, or less than about 22% followingexposure of about 500 hours to a strong acid solution at a temperatureof about 80° C. Even under harsher conditions, for instance in a 10%sulfuric acid solution held at a temperature of about 80° C. for 1000hours, the thermoplastic composition can maintain about 80% or more ofthe initial Charpy notched impact strength. The thermoplasticcomposition can also maintain desirable strength characteristicsfollowing exposure to other potentially degrading materials, such assalts, e.g., road salts as may be encountered in automotiveapplications.

FIG. 4 illustrates a schematic of a process that can be used in formingthe thermoplastic composition. As illustrated, the components of thethermoplastic composition may be melt-kneaded in a melt processing unitsuch as an extruder 100. Extruder 100 can be any extruder as is known inthe art including, without limitation, a single, twin, or multi-screwextruder, a co-rotating or counter rotating extruder, an intermeshing ornon-intermeshing extruder, and so forth. In one embodiment, thecomposition may be melt processed in an extruder 100 that includesmultiple zones or barrels. In the illustrated embodiment, extruder 100includes 10 barrels numbered 21-30 along the length of the extruder 100,as shown. Each barrel 21-30 can include feed lines 14, 16, vents 12,temperature controls, etc. that can be independently operated. A generalpurpose screw design can be used to melt process the polyarylenecomposition. By way of example, a thermoplastic composition may be meltmixed using a twin screw extruder such as a Coperion co-rotating fullyintermeshing twin screw extruder.

In forming a thermoplastic composition, the polyarylene sulfide can befed to the extruder 100 at a main feed throat 14. For instance, thepolyarylene sulfide may be fed to the main feed throat 14 at the firstbarrel 21 by means of a metering feeder. The polyarylene sulfide can bemelted and mixed with the other components of the composition as itprogresses through the extruder 100. The impact modifier can be added tothe composition in conjunction with the thermoplastic composition at themain feed throat 14 or downstream of the main feed throat, as desired.

At a point downstream of the main feed throat 14, and following additionof the impact modifier to the composition, the crosslinking agent can beadded to the composition. For instance, in the illustrated embodiment, asecond feed line 16 at barrel 26 can be utilized for addition of thecrosslinking agent. The point of addition for the crosslinking agent isnot particularly limited. However, the crosslinking agent can be addedto the composition at a point after the polyarylene sulfide has beenmixed with the impact modifier under shear such that the impact modifieris well distributed throughout the polyarylene sulfide.

The polyarylene sulfide may be a polyarylene thioether containing repeatunits of the formula (I):

—[(Ar¹)_(n)—X]_(m)—[(Ar²)_(i)—Y]_(j)—[(Ar³)_(k)—Z]_(l)—[(Ar⁴)_(o)—W]_(p)—  (I)

wherein Ar¹, Ar², Ar³, and Ar⁴ are the same or different and are aryleneunits of 6 to 18 carbon atoms; W, X, Y, and Z are the same or differentand are bivalent linking groups selected from —SO₂—, —S—, —SO—, —CO—,—O—, —COO— or alkylene or alkylidene groups of 1 to 6 carbon atoms andwherein at least one of the linking groups is —S—; and n, m, i, j, k, l,o, and p are independently zero or 1, 2, 3, or 4, subject to the provisothat their sum total is not less than 2. The arylene units Ar¹, Ar²,Ar³, and Ar⁴ may be selectively substituted or unsubstituted.Advantageous arylene systems are phenylene, biphenylene, naphthylene,anthracene and phenanthrene. The polyarylene sulfide typically includesmore than about 30 mol %, more than about 50 mol %, or more than about70 mol % arylene sulfide (—S—) units. In one embodiment the polyarylenesulfide includes at least 85 mol % sulfide linkages attached directly totwo aromatic rings.

In one embodiment, the polyarylene sulfide is a polyphenylene sulfide,defined herein as containing the phenylene sulfide structure—(C₆H₄—S)_(n)— (wherein n is an integer of 1 or more) as a componentthereof.

The polyarylene sulfide may be synthesized prior to forming thethermoplastic composition, though this is not a requirement of aprocess, and a polyarylene sulfide can also be purchased from knownsuppliers. For instance Fortron® polyphenylene sulfide available fromTicona of Florence, Ky., USA can be purchased and utilized as thepolyarylene sulfide.

Synthesis techniques that may be used in making a polyarylene sulfideare generally known in the art. By way of example, a process forproducing a polyarylene sulfide can include reacting a material thatprovides a hydrosulfide ion, e.g., an alkali metal sulfide, with adihaloaromatic compound in an organic amide solvent.

The alkali metal sulfide can be, for example, lithium sulfide, sodiumsulfide, potassium sulfide, rubidium sulfide, cesium sulfide or amixture thereof. When the alkali metal sulfide is a hydrate or anaqueous mixture, the alkali metal sulfide can be processed according toa dehydrating operation in advance of the polymerization reaction. Analkali metal sulfide can also be generated in situ. In addition, a smallamount of an alkali metal hydroxide can be included in the reaction toremove or react impurities (e.g., to change such impurities to harmlessmaterials) such as an alkali metal polysulfide or an alkali metalthiosulfate, which may be present in a very small amount with the alkalimetal sulfide.

The dihaloaromatic compound can be, without limitation, ano-dihalobenzene, m-dihalobenzene, p-dihalobenzene, dihalotoluene,dihalonaphthalene, methoxy-dihalobenzene, dihalobiphenyl, dihalobenzoicacid, dihalodiphenyl ether, dihalodiphenyl sulfone, dihalodiphenylsulfoxide or dihalodiphenyl ketone. Dihaloaromatic compounds may be usedeither singly or in any combination thereof. Specific exemplarydihaloaromatic compounds can include, without limitation,p-dichlorobenzene; m-dichlorobenzene; o-dichlorobenzene;2,5-dichlorotoluene; 1,4-dibromobenzene; 1,4-dichloronaphthalene;1-methoxy-2,5-dichlorobenzene; 4,4′-dichlorobiphenyl;3,5-dichlorobenzoic acid; 4,4′-dichlorodiphenyl ether;4,4′-dichlorodiphenylsulfone; 4,4′-dichlorodiphenylsulfoxide; and4,4′-dichlorodiphenyl ketone.

The halogen atom can be fluorine, chlorine, bromine or iodine, and 2halogen atoms in the same dihalo-aromatic compound may be the same ordifferent from each other. In one embodiment, o-dichlorobenzene,m-dichlorobenzene, p-dichlorobenzene or a mixture of 2 or more compoundsthereof is used as the dihalo-aromatic compound.

As is known in the art, it is also possible to use a monohalo compound(not necessarily an aromatic compound) in combination with thedihaloaromatic compound in order to form end groups of the polyarylenesulfide or to regulate the polymerization reaction and/or the molecularweight of the polyarylene sulfide.

The polyarylene sulfide may be a homopolymer or may be a copolymer. By asuitable, selective combination of dihaloaromatic compounds, apolyarylene sulfide copolymer can be formed containing not less than twodifferent units. For instance, in the case where p-dichlorobenzene isused in combination with m-dichlorobenzene or4,4′-dichlorodiphenylsulfone, a polyarylene sulfide copolymer can beformed containing segments having the structure of formula (II):

and segments having the structure of formula (III):

or segments having the structure of formula (IV):

In general, the amount of the dihaloaromatic compound(s) per mole of theeffective amount of the charged alkali metal sulfide can generally befrom 1.0 to 2.0 moles, from 1.05 to 2.0 moles, or from 1.1 to 1.7 moles.Thus, the polyarylene sulfide can include alkyl halide (generally alkylchloride) end groups.

A process for producing the polyarylene sulfide can include carrying outthe polymerization reaction in an organic amide solvent. Exemplaryorganic amide solvents used in a polymerization reaction can include,without limitation, N-methyl-2-pyrrolidone; N-ethyl-2-pyrrolidone;N,N-dimethylformamide; N,N-dimethylacetamide; N-methylcaprolactam;tetramethylurea; dimethylimidazolidinone; hexamethyl phosphoric acidtriamide and mixtures thereof. The amount of the organic amide solventused in the reaction can be, e.g., from 0.2 to 5 kilograms per mole(kg/mol) of the effective amount of the alkali metal sulfide.

The polymerization can be carried out by a step-wise polymerizationprocess. The first polymerization step can include introducing thedihaloaromatic compound to a reactor, and subjecting the dihaloaromaticcompound to a polymerization reaction in the presence of water at atemperature of from about 180° C. to about 235° C., or from about 200°C. to about 230° C., and continuing polymerization until the conversionrate of the dihaloaromatic compound attains to not less than about 50mol % of the theoretically necessary amount.

In a second polymerization step, water is added to the reaction slurryso that the total amount of water in the polymerization system isincreased to about 7 moles, or to about 5 moles, per mole of theeffective amount of the charged alkali metal sulfide. Following, thereaction mixture of the polymerization system can be heated to atemperature of from about 250° C. to about 290° C., from about 255° C.to about 280° C., or from about 260° C. to about 270° C. and thepolymerization can continue until the melt viscosity of the thus formedpolymer is raised to the desired final level of the polyarylene sulfide.The duration of the second polymerization step can be, e.g., from about0.5 to about 20 hours, or from about 1 to about 10 hours.

The polyarylene sulfide may be linear, semi-linear, branched orcrosslinked. A linear polyarylene sulfide includes as the mainconstituting unit the repeating unit of —(Ar—S)—. In general, a linearpolyarylene sulfide may include about 80 mol % or more of this repeatingunit. A linear polyarylene sulfide may include a small amount of abranching unit or a cross-linking unit, but the amount of branching orcross-linking units may be less than about 1 mol % of the total monomerunits of the polyarylene sulfide. A linear polyarylene sulfide polymermay be a random copolymer or a block copolymer containing theabove-mentioned repeating unit.

A semi-linear polyarylene sulfide may be utilized that may have across-linking structure or a branched structure provided by introducinginto the polymer a small amount of one or more monomers having three ormore reactive functional groups. For instance between about 1 mol % andabout 10 mol % of the polymer may be formed from monomers having threeor more reactive functional groups. Methods that may be used in makingsemi-linear polyarylene sulfide are generally known in the art. By wayof example, monomer components used in forming a semi-linear polyarylenesulfide can include an amount of polyhaloaromatic compounds having 2 ormore halogen substituents per molecule which can be utilized inpreparing branched polymers. Such monomers can be represented by theformula R′X_(n), where each X is selected from chlorine, bromine, andiodine, n is an integer of 3 to 6, and R′ is a polyvalent aromaticradical of valence n which can have up to about 4 methyl substituents,the total number of carbon atoms in R′ being within the range of 6 toabout 16. Examples of some polyhaloaromatic compounds having more thantwo halogens substituted per molecule that can be employed in forming asemi-linear polyarylene sulfide include 1,2,3-trichlorobenzene,1,2,4-trichlorobenzene, 1,3-dichloro-5-bromobenzene,1,2,4-triiodobenzene, 1,2,3,5-tetrabromobenzene, hexachlorobenzene,1,3,5-trichloro-2,4,6-trimethylbenzene, 2,2′,4,4′-tetrachlorobiphenyl,2,2′,5,5′-tetra-iodobiphenyl,2,2′,6,6′-tetrabromo-3,3′,5,5′-tetramethylbiphenyl,1,2,3,4-tetrachloronaphthalene, 1,2,4-tribromo-6-methylnaphthalene, andthe like, and mixtures thereof.

Following polymerization, the polyarylene sulfide may be washed withliquid media. For instance, the polyarylene sulfide may be washed withwater and/or organic solvents that will not decompose the polyarylenesulfide including, without limitation, acetone, N-methyl-2-pyrrolidone,a salt solution, and/or an acidic media such as acetic acid orhydrochloric acid prior to combination with other components whileforming the mixture. The polyarylene sulfide can be washed in asequential manner that is generally known to persons skilled in the art.Washing with an acidic solution or a salt solution may reduce thesodium, lithium or calcium metal ion end group concentration from about2000 ppm to about 100 ppm.

A polyarylene sulfide can be subjected to a hot water washing process.The temperature of a hot water wash can be at or above about 100° C.,for instance higher than about 120° C., higher than about 150° C., orhigher than about 170° C.

The polymerization reaction apparatus for forming the polyarylenesulfide is not especially limited, although it is typically desired toemploy an apparatus that is commonly used in formation of high viscosityfluids. Examples of such a reaction apparatus may include a stirringtank type polymerization reaction apparatus having a stirring devicethat has a variously shaped stirring blade, such as an anchor type, amultistage type, a spiral-ribbon type, a screw shaft type and the like,or a modified shape thereof. Further examples of such a reactionapparatus include a mixing apparatus commonly used in kneading, such asa kneader, a roll mill, a Banbury mixer, etc. Following polymerization,the molten polyarylene sulfide may be discharged from the reactor,typically through an extrusion orifice fitted with a die of desiredconfiguration, cooled, and collected. Commonly, the polyarylene sulfidemay be discharged through a perforated die to form strands that aretaken up in a water bath, pelletized and dried. The polyarylene sulfidemay also be in the form of a strand, granule, or powder.

The thermoplastic composition may include the polyarylene sulfidecomponent (which also encompasses a blend of polyarylene sulfides) in anamount from about 10 wt. % to about 99 wt. % by weight of thecomposition, for instance from about 20% wt. % to about 90 wt. % byweight of the composition.

According to one embodiment, the polyarylene sulfide can befunctionalized to further encourage bond formation between thepolyarylene sulfide and the impact modifier and other additives as maybe included in the composition. For instance, a polyarylene sulfide canbe further treated following formation with a carboxyl, acid anhydride,amine, isocyanate or other functional group-containing modifyingcompound to provide a functional terminal group on the polyarylenesulfide. By way of example, a polyarylene sulfide can be reacted with amodifying compound containing a mercapto group or a disulfide group andalso containing a reactive functional group. In one embodiment, thepolyarylene sulfide can be reacted with the modifying compound in anorganic solvent. In another embodiment, the polyarylene sulfide can bereacted with the modifying compound in the molten state.

In one embodiment, a disulfide compound containing the desiredfunctional group can be incorporated into the thermoplastic compositionformation process, and the polyarylene sulfide can be functionalized inconjunction with formation of the composition. For instance, a disulfidecompound containing the desired reactive functional groups can be addedto the melt extruder in conjunction with the polyarylene sulfide or atany other point prior to or in conjunction with the addition of thecrosslinking agent.

Reaction between the polyarylene sulfide polymer and the reactivelyfunctionalized disulfide compound can include chain scission of thepolyarylene sulfide polymer that can decrease melt viscosity of thepolyarylene sulfide. In one embodiment, a higher melt viscositypolyarylene sulfide having low halogen content can be utilized as astarting polymer. Following reactive functionalization of thepolyarylene sulfide polymer by use of a functional disulfide compound, arelatively low melt viscosity polyarylene sulfide with low halogencontent can be formed. Following this chain scission, the melt viscosityof the polyarylene sulfide can be suitable for the injection molding,and the overall halogen content of the low melt viscosity polyarylenesulfide can be quite low. In one embodiment, the thermoplasticcomposition can have a halogen content of less than about 1000 ppm, lessthan about 900 ppm, less than about 600 ppm, or less than about 400 ppmas determined according to an elemental analysis using Parr Bombcombustion followed by Ion Chromatography.

The disulfide compound can generally have the structure of:

R¹—S—S—R²

wherein R¹ and R² may be the same or different and are hydrocarbongroups that independently include from 1 to about 20 carbons. Forinstance, R¹ and R² may be an alkyl, cycloalkyl, aryl, or heterocyclicgroup. R¹ and R¹ may include reactive functionality at terminal end(s)of the disulfide compound. For example, at least one of R¹ and R² mayinclude a terminal carboxyl group, hydroxyl group, a substituted ornon-substituted amino group, a nitro group, or the like. In general, thereactive functionality can be selected such that the reactivelyfunctionalized polyarylene sulfide can react with the impact modifier.For example, when considering an epoxy-terminated impact modifier, thedisulfide compound can include carboxyl and/or amine functionality.

Examples of disulfide compounds including reactive terminal groups asmay be encompassed herein may include, without limitation,2,2′-diaminodiphenyl disulfide, β,β′-diaminodiphenyl disulfide,4,4′-diaminodiphenyl disulfide, dibenzyl disulfide, dithiosalicyclicacid, dithioglycolic acid, α,α′-dithiodilactic acid, β,β′-dithiodilacticacid, 3,3′-dithiodipyridine, 4,4′dithiomorpholine,2,2′-dithiobis(benzothiazole), 2,2′-dithiobis(benzimidazole),2,2′-dithiobis(benzoxazole) and 2-(4′-morpholinodithio)benzothiazole.

The ratio of the amount of the polyarylene sulfide to the amount of thedisulfide compound can be from about 1000:1 to about 10:1, from about500:1 to about 20:1, or from about 400:1 to about 30:1.

In addition to the polyarylene sulfide polymer, the composition alsoincludes an impact modifier. More specifically, the impact modifier canbe an olefinic copolymer or terpolymer. For instance, the impactmodifier can include ethylenically unsaturated monomer units have fromabout 4 to about 10 carbon atoms.

The impact modifier can be modified to include functionalization so asto react with the crosslinking agent. For instance, the impact modifiercan be modified with a mole fraction of from about 0.01 to about 0.5 ofone or more of the following: an α, β unsaturated dicarboxylic acid orsalt thereof having from about 3 to about 8 carbon atoms; an α, βunsaturated carboxylic acid or salt thereof having from about 3 to about8 carbon atoms; an anhydride or salt thereof having from about 3 toabout 8 carbon atoms; a monoester or salt thereof having from about 3 toabout 8 carbon atoms; a sulfonic acid or a salt thereof; an unsaturatedepoxy compound having from about 4 to about 11 carbon atoms. Examples ofsuch modification functionalities include maleic anhydride, fumaricacid, maleic acid, methacrylic acid, acrylic acid, and glycidylmethacrylate. Examples of metallic acid salts include the alkaline metaland transitional metal salts such as sodium, zinc, and aluminum salts.

A non-limiting listing of impact modifiers that may be used includeethylene-acrylic acid copolymer, ethylene-maleic anhydride copolymers,ethylene-alkyl (meth)acrylate-maleic anhydride terpolymers,ethylene-alkyl (meth)acrylate-glycidyl (meth)acrylate terpolymers,ethylene-acrylic ester-methacrylic acid terpolymer, ethylene-acrylicester-maleic anhydride terpolymer, ethylene-methacrylic acid-methacrylicacid alkaline metal salt (ionomer) terpolymers, and the like. In oneembodiment, for instance, an impact modifier can include a randomterpolymer of ethylene, methylacrylate, and glycidyl methacrylate. Theterpolymer can have a glycidyl methacrylate content of from about 5% toabout 20%, such as from about 6% to about 10%. The terpolymer may have amethylacrylate content of from about 20% to about 30%, such as about24%.

According to one embodiment, the impact modifier may be a linear orbranched, homopolymer or copolymer (e.g., random, graft, block, etc.)containing epoxy functionalization, e.g., terminal epoxy groups,skeletal oxirane units, and/or pendent epoxy groups. For instance, theimpact modifier may be a copolymer including at least one monomercomponent that includes epoxy functionalization. The monomer units ofthe impact modifier may vary. In one embodiment, for example, the impactmodifier can include epoxy-functional methacrylic monomer units. As usedherein, the term methacrylic generally refers to both acrylic andmethacrylic monomers, as well as salts and esters thereof, e.g.,acrylate and methacrylate monomers. Epoxy-functional methacrylicmonomers as may be incorporated in the impact modifier may include, butare not limited to, those containing 1,2-epoxy groups, such as glycidylacrylate and glycidyl methacrylate. Other suitable epoxy-functionalmonomers include allyl glycidyl ether, glycidyl ethacrylate, andglycidyl itoconate.

Other monomer units may additionally or alternatively be a component ofthe impact modifier. Examples of other monomers may include, forexample, ester monomers, olefin monomers, amide monomers, etc. In oneembodiment, the impact modifier can include at least one linear orbranched α-olefin monomer, such as those having from 2 to 20 carbonatoms, or from 2 to 8 carbon atoms. Specific examples include ethylene;propylene; 1-butene; 3-methyl-1-butene; 3,3-dimethyl-1-butene;1-pentene; 1-pentene with one or more methyl, ethyl or propylsubstituents; 1-hexene with one or more methyl, ethyl or propylsubstituents; 1-heptene with one or more methyl, ethyl or propylsubstituents; 1-octene with one or more methyl, ethyl or propylsubstituents; 1-nonene with one or more methyl, ethyl or propylsubstituents; ethyl, methyl or dimethyl-substituted 1-decene;1-dodecene; and styrene.

Monomers included in an impact modifier that includes epoxyfunctionalization can include monomers that do not include epoxyfunctionalization, as long as at least a portion of the monomer units ofthe polymer are epoxy functionalized.

In one embodiment, the impact modifier can be a terpolymer that includesepoxy functionalization. For instance, the impact modifier can include amethacrylic component that includes epoxy functionalization, an α-olefincomponent, and a methacrylic component that does not include epoxyfunctionalization. For example, the impact modifier may bepoly(ethylene-co-methylacrylate-co-glycidyl methacrylate), which has thefollowing structure:

wherein, a, b, and c are 1 or greater.

In another embodiment the impact modifier can be a random copolymer ofethylene, ethyl acrylate and maleic anhydride having the followingstructure:

wherein x, y and z are 1 or greater.

The relative proportion of the various monomer components of acopolymeric impact modifier is not particularly limited. For instance,in one embodiment, the epoxy-functional methacrylic monomer componentscan form from about 1 wt. % to about 25 wt. %, or from about 2 wt. % toabout 20 wt % of a copolymeric impact modifier. An a-olefin monomer canform from about 55 wt. % to about 95 wt. %, or from about 60 wt. % toabout 90 wt. %, of a copolymeric impact modifier. When employed, othermonomeric components (e.g., a non-epoxy functional methacrylic monomers)may constitute from about 5 wt. % to about 35 wt. %, or from about 8 wt.% to about 30 wt. %, of a copolymeric impact modifier.

An impact modifier may be formed according to standard polymerizationmethods as are generally known in the art. For example, a monomercontaining polar functional groups may be grafted onto a polymerbackbone to form a graft copolymer. Alternatively, a monomer containingfunctional groups may be copolymerized with a monomer to form a block orrandom copolymer using known free radical polymerization techniques,such as high pressure reactions, Ziegler-Natta catalyst reactionsystems, single site catalyst (e.g., metallocene) reaction systems, etc.

Alternatively, an impact modifier may be obtained on the retail market.By way of example, suitable compounds for use as an impact modifier maybe obtained from Arkema under the name Lotader®.

The molecular weight of the impact modifier can vary widely. Forexample, the impact modifier can have a number average molecular weightfrom about 7,500 to about 250,000 grams per mole, in some embodimentsfrom about 15,000 to about 150,000 grams per mole, and in someembodiments, from about 20,000 to 100,000 grams per mole, with apolydispersity index typically ranging from 2.5 to 7.

In general, the impact modifier may be present in the composition in anamount from about 0.05% to about 40% by weight, from about 0.05% toabout 37% by weight, or from about 0.1% to about 35% by weight.

Referring again to FIG. 4, the impact modifier can be added to thecomposition in conjunction with the polyarylene sulfide at the main feedthroat 14 of the melt processing unit. This is not a requirement of thecomposition formation process, however, and in other embodiments, theimpact modifier can be added downstream of the main feed throat. Forinstance, the impact modifier may be added at a location downstream fromthe point at which the polyarylene sulfide is supplied to the meltprocessing unit, but yet prior to the melting section, i.e., that lengthof the melt processing unit in which the polyarylene sulfide becomesmolten. In another embodiment, the impact modifier may be added at alocation downstream from the point at which the polyarylene sulfidebecomes molten.

If desired, one or more distributive and/or dispersive mixing elementsmay be employed within the mixing section of the melt processing unit.Suitable distributive mixers for single screw extruders may include butare not limited to, for instance, Saxon, Dulmage, Cavity Transfermixers, etc. Likewise, suitable dispersive mixers may include but arenot limited to Blister ring, Leroy/Maddock, CRD mixers, etc. As is wellknown in the art, the mixing may be further improved by using pins inthe barrel that create a folding and reorientation of the polymer melt,such as those used in Buss Kneader extruders, Cavity Transfer mixers,and Vortex Intermeshing Pin mixers.

In addition to the polyarylene sulfide and the impact modifier, thepolyarylene composition can include a crosslinking agent. Thecrosslinking agent can be a polyfunctional compound or combinationthereof that can react with functionality of the impact modifier to formcrosslinks within and among the polymer chains of the impact modifier.In general, the crosslinking agent can be a non-polymeric compound,i.e., a molecular compound that includes two or more reactivelyfunctional terminal moieties linked by a bond or a non-polymeric(non-repeating) linking component. By way of example, the crosslinkingagent can include but is not limited to di-epoxides, poly-functionalepoxides, diisocyanates, polyisocyanates, polyhydric alcohols,water-soluble carbodiimides, diamines, diaminoalkanes, polyfunctionalcarboxylic acids, diacid halides, and so forth. For instance, whenconsidering an epoxy-functional impact modifier, a non-polymericpolyfunctional carboxylic acid or amine can be utilized as acrosslinking agent.

Specific examples of polyfunctional carboxylic acid crosslinking agentscan include, without limitation, isophthalic acid, terephthalic acid,phthalic acid, 1,2-di(p-carboxyphenyl)ethane, 4,4′-dicarboxydiphenylether, 4,4′-bisbenzoic acid, 1,4- or 1,5-naphthalene dicarboxylic acids,decahydronaphthalene dicarboxylic acids, norbornene dicarboxylic acids,bicyclooctane dicarboxylic acids, 1,4-cyclohexanedicarboxylic acid (bothcis and trans), 1,4-hexylenedicarboxylic acid, adipic acid, azelaicacid, dicarboxyl dodecanoic acid, succinic acid, maleic acid, glutaricacid, suberic acid, azelaic acid and sebacic acid. The correspondingdicarboxylic acid derivatives, such as carboxylic acid diesters havingfrom 1 to 4 carbon atoms in the alcohol radical, carboxylic acidanhydrides or carboxylic acid halides may also be utilized.

Exemplary diols useful as crosslinking agents can include, withoutlimitation, aliphatic diols such as ethylene glycol, 1,2-propyleneglycol, 1,3-propylene glycol, 2,2-dimethyl-1,3-propane diol,2-ethyl-2-methyl-1,3-propane diol, 1,4-butane diol, 1,4-but-2-ene diol,1,3-1,5-pentane diol, 1,5-pentane diol, dipropylene glycol,2-methyl-1,5-pentane diol, and the like. Aromatic diols can also beutilized such as, without limitation, hydroquinone, catechol,resorcinol, methylhydroquinone, chlorohydroquinone, bisphenol A,tetrachlorobisphenol A, phenolphthalein, and the like. Exemplarycycloaliphatic diols as may be used include a cycloaliphatic moiety, forexample 1,6-hexane diol, dimethanol decalin, dimethanol bicyclooctane,1,4-cyclohexane dimethanol (including its cis- and trans-isomers),triethylene glycol, 1,10-decanediol, and the like.

Exemplary diamines that may be utilized as crosslinking agents caninclude, without limitation, isophorone-diamine, ethylenediamine, 1,2-,1,3-propylene-diamine, N-methyl-1,3-propylene-diamine,N,N′-dimethyl-ethylene-diamine, and aromatic diamines, such as, forexample, 2,4- and 2,6-toluoylene-diamine, 3,5-diethyl-2,4- and/or-2,6-toluoylene-diamine, and primary ortho- di-, tri- and/ortetra-alkyl-substituted 4,4′-diam inodiphenyl-methanes, (cyclo)aliphaticdiamines, such as, for example, isophorone-diamine, ethylenediamine,1,2-, 1,3-propylene-diamine, N-methyl-1,3-propylene-diamine,N,N′-dimethyl-ethylene-diamine, and aromatic diamines, such as, forexample, 2,4- and 2,6-toluoylene-diamine, 3,5-diethyl-2,4- and/or-2,6-toluoylene-diamine, and primary ortho- di-, tri- and/ortetra-alkyl-substituted 4,4′-diam inodiphenyl-methanes.

In one embodiment, the composition can include a disulfide-freecrosslinking agent. For example, the crosslinking agent can includecarboxyl and/or amine functionality with no disulfide group that mayreact with the polyarylene sulfide. A crosslinking agent that isdisulfide-free can be utilized so as to avoid excessive chain scissionof the polyarylene sulfide by the crosslinking agent during formation ofthe composition. It should be understood, however, that the utilizationof a disulfide-free crosslinking agent does not in any way limit theutilization of a reactively functionalized disulfide compound forfunctionalizing the polyarylene sulfide. For instance, in oneembodiment, the composition can be formed according to a process thatincludes addition of a reactively functionalized disulfide compound tothe melt processing unit that can reactively functionalize thepolyarylene sulfide. The crosslinking agent utilized in this embodimentcan then be a disulfide-free crosslinking agent that can includefunctionality that is reactive with the impact modifier as well as withthe reactively functionalized polyarylene sulfide. Thus, the compositioncan be highly crosslinked without excessive scission of the polyarylenesulfide polymer chains.

In another embodiment the crosslinking agent and the polyarylene sulfidefunctionalization compound (when present) can be selected so as toencourage chain scission of the polyarylene sulfide. This may bebeneficial, for instance, which chain scission is desired to decreasethe melt viscosity of the polyarylene sulfide polymer.

The thermoplastic composition may generally include the crosslinkingagent in an amount from about 0.05 wt. % to about 2 wt. % by weight ofthe thermoplastic composition, from about 0.07 wt. % to about 1.5 wt. %by weight of the thermoplastic composition, or from about 0.1 wt. % toabout 1.3 wt. %.

The crosslinking agent can be added to the melt processing unitfollowing mixing of the polyarylene sulfide and the impact modifier. Forinstance, as illustrated in FIG. 4, the crosslinking agent can be addedto the composition at a downstream location 16 following addition ofpolyarylene sulfide and the impact modifier (either together orseparately) to the melt processing unit. This can ensure that the impactmodifier has become dispersed throughout the polyarylene sulfide priorto addition of the crosslinking agent.

To help encourage distribution of the impact modifier throughout themelt prior to addition of the crosslinking agent, a variety of differentparameters may be selectively controlled. For example, the ratio of thelength (“L”) to diameter (“D”) of a screw of the melt processing unitmay be selected to achieve an optimum balance between throughput andimpact modifier distribution. For example, the L/D value after the pointat which the impact modifier is supplied may be controlled to encouragedistribution of the impact modifier. More particularly, the screw has ablending length (“L_(B)”) that is defined from the point at which boththe impact modifier and the polyarylene sulfide are supplied to the unit(i.e., either where they are both supplied in conjunction with oneanother or the point at which the latter of the two is supplied) to thepoint at which the crosslinking agent is supplied, the blending lengthgenerally being less than the total length of the screw. For example,when considering a melt processing unit that has an overall L/D of 40,the L_(B)/D ratio of the screw can be from about 1 to about 36, in someembodiments from about 4 to about 20, and in some embodiments, fromabout 5 to about 15. In one embodiment, the L/L_(B) ratio can be fromabout 40 to about 1.1, from about 20 to about 2, or from about 10 toabout 5.

Following addition of the crosslinking agent, the composition can bemixed to distribute the crosslinking agent throughout the compositionand encourage reaction between the crosslinking agent, the impactmodifier, and, in one embodiment, with the polyarylene sulfide.

Optionally, the thermoplastic composition can include one or moreadditional polymers. For instance, in one embodiment the thermoplasticcomposition can also include a siloxane polymer. The siloxane polymercan encompass any polymer, co-polymer or oligomer that includes siloxaneunits in the backbone having the formula:

wherein R₃ and R₄ are independently of one another, hydrogen, alkyl,alkenyl, acyl, alkaryl or aralkyl having up to 20 carbon atoms. In oneembodiment the siloxane polymer includes reactive functionality on atleast a portion of the siloxane monomer units of the polymer. Thebackbone of the siloxane polymer can include substitutions as is knownin the art such as alkyl substitutions, phenyl substitutions, etc.

Some examples of suitable siloxane polymers include, without limitation,polydimethyl siloxanes such as dimethylvinylsiloxy end group-cappedpolydimethyl siloxane, methyldivinylsiloxy end group-capped polydimethylsiloxane, dimethylvinylsiloxy end group-capped dimethyl siloxane, (80mol %)/methylphenylsiloxane (20 mol %) copolymers, dimethylvinylsiloxyend group-capped dimethylsiloxane (80 mol %)/diphenylsiloxane (20 mol %)copolymers, dimethylvinylsiloxy end group-capped dimethylsiloxane (90mol %)/diphenylsiloxane (10 mol %) copolymers, and trimethylsiloxy endgroup-capped dimethylsiloxane/methylvinylsiloxane copolymers. Besidesthe above-mentioned polymers, other polymers may also be utilized. Forinstance, some suitable vinyl-modified silicones include, but are notlimited to, vinyldimethyl terminated polydimethylsiloxanes; vinylmethyl,dimethylpolysiloxane copolymers; vinyldimethyl terminated vinylmethyl,dimethylpolysiloxane copolymers; divinylmethyl terminatedpolydimethylsiloxanes; polydimethylsiloxane, mono vinyl, monon-butyldimethyl terminated; and vinylphenylmethyl terminatedpolydimethylsiloxanes. Further, some methyl-modified silicones that canbe used include, but are not limited to, dimethylhydro terminatedpolydimethylsiloxanes; methylhydro, dimethylpolysiloxane copolymers;methylhydro terminated methyloctyl siloxane copolymers; and methylhydro,phenylmethyl siloxane copolymers.

When included, the reactive functionality of the siloxane polymer caninclude, without limitation, one or more of vinyl groups, hydroxylgroups, hydrides, isocyanate groups, epoxy groups, acid groups, halogenatoms, alkoxy groups (e.g., methoxy, ethoxy and propoxy), acyloxy groups(e.g., acetoxy and octanoyloxy), ketoximate groups (e.g.,dimethylketoxime, methylketoxime and methylethylketoxime), amino groups(e.g., dimethylamino, diethylamino and butylamino), amido groups (e.g.,N-methylacetamide and N-ethylacetamide), acid amido groups, amino-oxygroups, mercapto groups, alkenyloxy groups (e.g., vinyloxy,isopropenyloxy, and 1-ethyl-2-methylvinyloxy), alkoxyalkoxy groups(e.g., methoxyethoxy, ethoxyethoxy and methoxypropoxy), aminoxy groups(e.g., dimethylaminoxy and diethylaminoxy), mercapto groups, and thelike.

The siloxane polymer can have any desired molecular weight. For example,in one embodiment, the siloxane polymer can have a molecular weight ofgreater than about 5000. In one embodiment, a high molecular weightsiloxane polymer can be incorporated in the thermoplastic composition,e.g., a high molecular weight polydimethylsiloxane that can have morethan about 200 —(CH₃)₂ SiO— repeating units along the backbone. Inanother embodiment, an ultrahigh molecular weight siloxane polymer,e.g., an ultrahigh molecular weight polydimethylsiloxane can beincorporated in the thermoplastic composition that can have a numberaverage molecular weight of about 10⁶ grams per mole or greater.

In one embodiment, the siloxane polymer can be epoxy-functionalized andcan include epoxy groups incorporated into the siloxane polymer havingthe formula:

wherein R₅ is a divalent aliphatic (C₁-C₁₀), cycloalkyl(C₅-C₂₀)heterocyclic (C₄-C₉), substituted or unsubstituted aromatic (C₆-C₉)hydrocarbon radical or a direct bond.

The epoxy groups can be incorporated onto an amine-functionalized oramino-terminated siloxane. For instance, an amine-terminated siloxanepolymer such as those available commercially as the “G series” siloxaneresins available from the General Electric Company can be reactivelyfunctionalized with epoxy. Epoxy functionalization may be carried outvia reaction with an epoxy-containing compound such as an epoxychlorotriazine as is known. One example of a suitable epoxychlorotriazine as may be utilized is trimethylglycidyl cyanuricchloride.

Reaction between the epoxy chlorotriazine and the siloxane may beconducted in an organic solvent such as toluene, methylene chloride, orother organic liquid of similar polarity. Reaction temperatures in therange of about 20° C. to about 100° C. may be employed. Excess amountsof the epoxy chlorotriazine are typically employed, which fall in therange of between about 1% and about 6% or between about 2% and about 6%by weight of the siloxane polymer.

A siloxane polymer can be mercapto-functionalized and can includemercapto groups incorporated into the siloxane polymer having theformula:

wherein R₅ is as described above. For example, the siloxane polymer canbe a mercapto-functionalized polydimethyl siloxane having the generalformula:

When incorporated in the thermoplastic composition, the composition caninclude a siloxane polymer in an amount of about 40 wt. % or less of thethermoplastic composition. For instance, the thermoplastic compositioncan include a siloxane polymer in an amount of from about 0.05 wt. % toabout 35 wt. %, or about 0.1 wt. % to about 30 wt. %. A siloxane polymercan be incorporated in the thermoplastic composition at any point duringthe formation process, for instance in the main feed in conjunction withthe polyarylene sulfide or downstream.

In combination with the siloxane polymer, the thermoplastic compositioncan include fumed silica. Fumed silica can generally have a particlesize of from about 5 nanometers to about 50 nanometers. The particlesare non-porous and can have a surface area of from about 50 squaremeters per gram (m²/g) to about 600 m²/g and a density of from about 160kilogram per cubic meter (kg/m³) to about 190 kg/m³. When incorporatedin the thermoplastic composition, the composition can include fumedsilica in an about of less than about 25 wt. %, for instance from about0.05 wt % to about 20 wt. %. In one embodiment, the fumed silica can becombined with the siloxane polymer prior to addition of this mixture tothe thermoplastic composition. For instance a mixture including anultrahigh molecular weight polydimethylsiloxane and fumed silica can beincorporated in the thermoplastic composition. Such a pre-formed mixtureis available as Genioplast® from Wacker Chemie, AG.

The composition can include a coupling agent, for instance inconjunction with the siloxane polymer and can function to form bondsbetween and among the siloxane polymer and/or to couple the siloxanepolymer to other components of the composition, such as the polyarylenesulfide, in one embodiment. The coupling agent can be any coupling agentas is known in the art that includes a silicon, zirconium, titanate, orother multireactive group chemistry. In one embodiment, the couplingagent can be an organosilane coupling agent, and in particular may be analkoxy silane coupling agent as is known in the art including monoalkoxysilanes, dialkoxysilanes, chorlor silanes, and the like. For example,silane coupling agents available from Gelest, Inc. of Morrisville, Pa.can be utilized. The alkoxysilane compound may be a silane compoundselected from, and without limitation to, vinlyalkoxysilanes,epoxyalkoxysilanes, am inoalkoxysilanes, mercaptoalkoxysilanes, andcombinations thereof. Examples of the vinylalkoxysilane that may beutilized include vinyltriethoxysilane, vinyltrimethoxysilane andvinyltris(β-methoxyethoxy)silane. Examples of the epoxyalkoxysilanesthat may be used include γ-glycidoxypropyltrimethoxysilane,β-(3,4-epoxycyclohexyl) ethyltrimethoxysilane andγ-glycidoxypropyltriethoxysilane. Examples of the mercaptoalkoxysilanesthat may be employed include γ-mercaptopropyltrimethoxysilane andγ-mercaptopropyltriethoxysilane.

Amino silane compounds that may be included are typically of theformula: R⁷—Si—(R⁸)₃, wherein R⁷ is selected from the group consistingof an amino group such as NH₂; an aminoalkyl of from about 1 to about 10carbon atoms, or from about 2 to about 5 carbon atoms, such asaminomethyl, aminoethyl, aminopropyl, aminobutyl, and so forth; analkene of from about 2 to about 10 carbon atoms, or from about 2 toabout 5 carbon atoms, such as ethylene, propylene, butylene, and soforth; and an alkyne of from about 2 to about 10 carbon atoms, or fromabout 2 to about 5 carbon atoms, such as ethyne, propyne, butyne and soforth; and wherein R⁸ is an alkoxy group of from about 1 to about 10atoms, or from about 2 to about 5 carbon atoms, such as methoxy, ethoxy,propoxy, and so forth.

In one embodiment, R⁷ is selected from the group consisting ofaminomethyl, aminoethyl, aminopropyl, ethylene, ethyne, propylene andpropyne, and R⁸ is selected from the group consisting of methoxy groups,ethoxy groups, and propoxy groups. In another embodiment, R⁷ is selectedfrom the group consisting of an alkene of from about 2 to about 10carbon atoms such as ethylene, propylene, butylene, and so forth, and analkyne of from about 2 to about 10 carbon atoms such as ethyne, propyne,butyne and so forth, and R⁸ is an alkoxy group of from about 1 to about10 atoms, such as methoxy group, ethoxy group, propoxy group, and soforth. A combination of various aminosilanes may also be included in thepolyarylene sulfide composition.

Some representative examples of amino silane coupling agents that may beincluded in the polyarylene sulfide composition include aminopropyltriethoxy silane, aminoethyl triethoxy silane, aminopropyl trimethoxysilane, aminoethyl trimethoxy silane, ethylene trimethoxy silane,ethylene triethoxy silane, ethyne trimethoxy silane, ethyne triethoxysilane, aminoethylaminopropyltrimethoxy silane, 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxy silane, 3-aminopropyl methyldimethoxysilane or 3-aminopropyl methyl diethoxy silane,N-(2-aminoethyl)-3-aminopropyl trimethoxy silane, N-methyl-3-aminopropyltrimethoxy silane, N-phenyl-3-aminopropyl trimethoxy silane,bis(3-aminopropyl) tetramethoxy silane, bis(3-aminopropyl) tetraethoxydisiloxane, and combinations thereof. The amino silane may also be anaminoalkoxysilane, such as γ-aminopropyltrimethoxysilane,γ-aminopropyltriethoxysilane, γ-aminopropylmethyldimethoxysilane,γ-aminopropylmethyldiethoxysilane,N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane,N-phenyl-γ-aminopropyltrimethoxysilane,γ-diallylaminopropyltrimethoxysilane andγ-diallylaminopropyltrimethoxysilane. One suitable amino silane is3-aminopropyltriethoxysilane which is available from Degussa, SigmaChemical Company, and Aldrich Chemical Company.

Beneficially, a relatively small amount of the silane coupling agent canbe incorporated into the thermoplastic composition, which can be verycost effective. For example, the polyarylene sulfide composition caninclude less than about 3% by weight of the silane coupling agent, forinstance between about 0.05% and about 3% by weight of the silanecoupling agent. In one embodiment, the composition can include fromabout 0.1% to about 2.5%, or from about 1% to about 2% by weight of thesilane coupling agent.

In one embodiment the thermoplastic composition can incorporate athermoplastic elastomer. Thermoplastic elastomers have some physicalproperties of rubber, such as softness, flexibility and resilience, butmay be processed like thermoplastics. A transition from a melt to asolid rubber-like composition occurs fairly rapidly upon cooling. Thisis in contrast to conventional elastomers, which harden slowly uponheating. Thermoplastic elastomers may be processed on injection moldersand extruders and thus can be beneficially incorporated in thethermoplastic composition.

The thermoplastic elastomer can be a block copolymer in which at leastone phase is made of a material that is hard at room temperature butfluid upon heating. Another phase is a softer material that isrubber-like at room temperature. The thermoplastic elastomer can have anA-B-A block copolymer structure, where A represents hard segments and Bis a soft segment. In another embodiment, the thermoplastic elastomercan have a repeating structure represented by (A-B)_(n), where Arepresents the hard segments and B the soft segments as described above.

Non-limiting examples of thermoplastic elastomers having a (A-B),repeating structure include polyamide/polyether,polysulfone/polydimethylsiloxane, polyurethane/polyester,polyurethane/polyether, polyester/polyether,polycarbonate/polydimethylsiloxane, and polycarbonate/polyether.Triblock elastomers can be utilized with polystyrene as the hard segmentand either polybutadiene, polyisoprene, or polyethylene-co-butylene asthe soft segment. Similarly, styrene butadiene repeating co-polymers canbe utilized, as well as polystyrene/polyisoprene repeating polymers.

In one particular embodiment, a thermoplastic elastomer can be used thathas alternating blocks of polyamide and polyether. Such materials arecommercially available, for example from Atofina under the Pebax™ tradename. The polyamide blocks may be derived from a copolymer of a diacidcomponent and a diamine component, or may be prepared byhomopolymerization of a cyclic lactam. The polyether block is generallyderived from homo- or copolymers of cyclic ethers such as ethyleneoxide, propylene oxide, and tetrahydrofuran.

When included, the thermoplastic composition can include thethermoplastic elastomer in an amount of about 40 wt. % or less of thethermoplastic composition. For instance, the thermoplastic compositioncan include a siloxane polymer in an amount of from about 0.05 wt. % toabout 35 wt. %, or about 0.1 wt. % to about 30 wt. %.

The composition can also include one or more additives as are generallyknown in the art. For example, one or more fillers can be included inthe thermoplastic composition. One or more fillers may generally beincluded in the thermoplastic composition an amount of from about 5 wt.% to about 70 wt. %, or from about 20 wt. % to about 65 wt. % by weightof the thermoplastic composition.

The filler can be added to the thermoplastic composition according tostandard practice. For instance, the filler can be added to thecomposition at a downstream location of the melt processing unit. Forexample, a filler may be added to the composition in conjunction withthe addition of the crosslinking agent. However, this is not arequirement of a formation process and the filler can be addedseparately from the crosslinking agent and either upstream or downstreamof the point of addition of the crosslinking agent. In addition, afiller can be added at a single feed location, or may be split and addedat multiple feed locations along the melt processing unit.

In one embodiment, a fibrous filler can be included in the thermoplasticcomposition. The fibrous filler may include one or more fiber typesincluding, without limitation, polymer fibers, glass fibers, carbonfibers, metal fibers, basalt fibers, and so forth, or a combination offiber types. In one embodiment, the fibers may be chopped fibers,continuous fibers, or fiber rovings (tows).

Fiber sizes can vary as is known in the art. In one embodiment, thefibers can have an initial length of from about 3 mm to about 5 mm. Inanother embodiment, for instance when considering a pultrusion process,the fibers can be continuous fibers. Fiber diameters can vary dependingupon the particular fiber used. The fibers, for instance, can have adiameter of less than about 100 μm, such as less than about 50 μm. Forinstance, the fibers can be chopped or continuous fibers and can have afiber diameter of from about 5 μm to about 50 μm, such as from about 5μm to about 15 μm.

The fibers may be pretreated with a sizing as is generally known. In oneembodiment, the fibers may have a high yield or small K numbers. The towis indicated by the yield or K number. For instance, glass fiber towsmay have 50 yield and up, for instance from about 115 yield to about1200 yield.

Other fillers can alternatively be utilized or may be utilized inconjunction with a fibrous filler. For instance, a particulate fillercan be incorporated in the thermoplastic composition. In general,particulate fillers can encompass any particulate material having amedian particle size of less than about 750 μm, for instance less thanabout 500 μm, or less than about 100 μm. In one embodiment, aparticulate filler can have a median particle size in the range of fromabout 3 μm to about 20 μm. In addition, a particulate filler can besolid or hollow, as is known. Particulate fillers can also include asurface treatment, as is known in the art.

Particulate fillers can encompass one or more mineral fillers. Forinstance, the thermoplastic composition can include one or more mineralfillers in an amount of from about 1 wt. % to about 60 wt. % of thecomposition. Mineral fillers may include, without limitation, silica,quartz powder, silicates such as calcium silicate, aluminum silicate,kaolin, talc, mica, clay, diatomaceous earth, wollastonite, calciumcarbonate, and so forth.

When incorporating multiple fillers, for instance a particulate fillerand a fibrous filler, the fillers may be added together or separately tothe melt processing unit. For instance, a particulate filler can beadded to the main feed with the polyarylene sulfide or downstream priorto addition of a fibrous filler, and a fibrous filler can be addedfurther downstream of the addition point of the particulate filler. Ingeneral, a fibrous filler can be added downstream of any other fillerssuch as a particulate filler, though this is not a requirement.

In one embodiment, the thermoplastic composition can include a UVstabilizer as an additive. For instance, the thermoplastic compositioncan include a UV stabilizer in an amount of between about 0.5 wt. % andabout 15 wt. %, between about 1 wt. % and about 8 wt. %, or betweenabout 1.5 wt. % and about 7 wt. % of a UV stabilizer. One particularlysuitable UV stabilizer that may be employed is a hindered amine UVstabilizer. Suitable hindered amine UV stabilizer compounds may bederived from a substituted piperidine, such as alkyl-substitutedpiperidyl, piperidinyl, piperazinone, alkoxypiperidinyl compounds, andso forth. For example, the hindered amine may be derived from a2,2,6,6-tetraalkylpiperidinyl. The hindered amine may, for example, bean oligomeric or polymeric compound having a number average molecularweight of about 1,000 or more, in some embodiments from about 1000 toabout 20,000, in some embodiments from about 1500 to about 15,000, andin some embodiments, from about 2000 to about 5000. Such compoundstypically contain at least one 2,2,6,6-tetraalkylpiperidinyl group(e.g., 1 to 4) per polymer repeating unit. One particularly suitablehigh molecular weight hindered amine is commercially available fromClariant under the designation Hostavin® N30 (number average molecularweight of 1200). Another suitable high molecular weight hindered amineis commercially available from Adeka Palmarole SAS under the designationADK STAB® LA-63 and ADK STAB® LA-68.

In addition to the high molecular hindered amines, low molecular weighthindered amines may also be employed. Such hindered amines are generallymonomeric in nature and have a molecular weight of about 1000 or less,in some embodiments from about 155 to about 800, and in someembodiments, from about 300 to about 800.

Other suitable UV stabilizers may include UV absorbers, such asbenzotriazoles or benzopheones, which can absorb UV radiation.

An additive that may be included in a thermoplastic composition is oneor more colorants as are generally known in the art. For instance, thethermoplastic composition can include from about 0.1 wt. % to about 10wt. %, or from about 0.2 wt. % to about 5 wt. % of one or morecolorants. As utilized herein, the term “colorant” generally refers toany substance that can impart color to a material. Thus, the term“colorant” encompasses both dyes, which exhibit solubility in an aqueoussolution, and pigments, that exhibit little or no solubility in anaqueous solution.

Examples of dyes that may be used include, but are not limited to,disperse dyes. Suitable disperse dyes may include those described in“Disperse Dyes” in the Color Index, 3^(rd) edition. Such dyes include,for example, carboxylic acid group-free and/or sulfonic acid group-freenitro, amino, aminoketone, ketoninime, methine, polymethine,diphenylamine, quinoline, benzimidazole, xanthene, oxazine and coumarindyes, anthraquinone and azo dyes, such as mono- or di-azo dyes. Dispersedyes also include primary red color disperse dyes, primary blue colordisperse dyes, and primary yellow color dyes.

Pigments that can be incorporated in a thermoplastic composition caninclude, without limitation, organic pigments, inorganic pigments,metallic pigments, phosphorescent pigments, fluorescent pigments,photochromic pigments, thermochromic pigments, iridescent pigments, andpearlescent pigments. The specific amount of pigment can depends uponthe desired final color of the product. Pastel colors are generallyachieved with the addition of titanium dioxide white or a similar whitepigment to a colored pigment.

Other additives that can be included in the thermoplastic compositioncan encompass, without limitation, antimicrobials, lubricants,antioxidants, stabilizers (e.g., heat stabilizers includingorganophosphites such as Doverphos® products available from DoverChemical Corporation), surfactants, flow promoters, solid solvents, andother materials added to enhance properties and processability. Suchoptional materials may be employed in the thermoplastic composition inconventional amounts and according to conventional processingtechniques, for instance through addition to the thermoplasticcomposition at the main feed throat. Beneficially, the thermoplasticcomposition can exhibit desirable characteristics without the additionof plasticizers. For instance, the composition can be free ofplasticizers such as phthalate esters, trimellitates, sebacates,adipates, gluterates, azelates, maleates, benzoates, and so forth.

Following addition of all components to the thermoplastic composition,the composition is thoroughly mixed in the remaining section(s) of theextruder and extruded through a die. The final extrudate can bepelletized or directly injection molded.

The method of the present invention includes the injection of thethermoplastic composition into a mold cavity where it is cooled untilreaching the desired ejection temperature. As is known in the art,injection can occur in two main phases—i.e., an injection phase andholding phase. During the injection phase, the mold cavity is completelyfilled with the molten thermoplastic composition. The holding phase isinitiated after completion of the injection phase in which the holdingpressure is controlled to pack additional material into the cavity andcompensate for volumetric shrinkage that occurs during cooling. Afterthe shot has built, it can then be cooled. Once cooling is complete, themolding cycle is completed when the mold opens and the part is ejected,such as with the assistance of ejector pins within the mold.

Any suitable injection molding equipment may generally be employed inthe present invention. Referring to FIG. 5, for example, one embodimentof an injection molding apparatus or tool 110 that may be employed inthe present invention is shown. In this embodiment, the apparatus 110includes a first mold base 112 and a second mold base 114, whichtogether define an article or component-defining mold cavity 116. Themolding apparatus 110 also includes a resin flow path that extends froman outer exterior surface 120 of the first mold half 112 through a sprue122 to a mold cavity 116. The resin flow path may also include a runnerand a gate, both of which are not shown for purposes of simplicity. Thethermoplastic composition may be supplied to the resin flow path using avariety of techniques. For example, the thermoplastic composition may besupplied (e.g., in the form of pellets) to a feed hopper attached to anextruder barrel that contains a rotating screw (not shown). As the screwrotates, the pellets are moved forward and undergo pressure andfriction, which generates heat to melt the pellets. Additional heat mayalso be supplied to the composition by a heating medium that iscommunication with the extruder barrel. One or more ejector pins 124 mayalso be employed that are slidably secured within the second mold half114 to define the mold cavity 116 in the closed position of theapparatus 110. The ejector pins 124 operate in a well-known fashion toremove a molded part from the cavity 116 in the open position of themolding apparatus 110.

A cooling mechanism may also be provided to solidify the resin withinthe mold cavity. In FIG. 5, for instance, the mold bases 112 and 114each include one or more cooling lines 118 through which a coolingmedium flows to impart the desired mold temperature to the surface ofthe mold bases for solidifying the molten material.

Embodiments of the present disclosure are illustrated by the followingexamples that are merely for the purpose of illustration of embodimentsand are not to be regarded as limiting the scope of the invention or themanner in which it may be practiced. Unless specifically indicatedotherwise, parts and percentages are given by weight.

Test Methods

Tensile Properties:

Tensile properties including tensile modulus, yield stress, yieldstrain, strength at break, elongation at yield, elongation at break,etc. are tested according to ISO Test No. 527 (technically equivalent toASTM D638). Modulus, strain, and strength measurements are made on thesame test strip sample having a length of 80 mm, thickness of 10 mm, andwidth of 4 mm. The testing temperature is 23° C., and the testing speedsare 5 or 50 mm/min.

Notched Charpy Impact Strength:

Notched Charpy properties are tested according to ISO Test No. ISO179-1) (technically equivalent to ASTM D256, Method B). This test is runusing a Type A notch (0.25 mm base radius) and Type 1 specimen size(length of 80 mm, width of 10 mm, and thickness of 4 mm). Specimens arecut from the center of a multi-purpose bar using a single tooth millingmachine. The testing temperature is 23° C., −30° F., or −40° F. asreported below.

Example 1

A polyphenylene sulfide (Fortron® 0214, available from Ticona) wastumble blended with a mixture of an ultrahigh molecular weightpolydimethylsiloxane and fumed silica (Genioplast® Pellet S availablefrom Wacker Chemie AG) and in one sample also with an aminosilanecoupling agent. The mixture was melt extruded through a WLE-25 mm at310° C. and pelletized. The formulation and mechanical property testingresults are shown in the table, below.

Sample No. 1 2 3 Components Polyphenylene sulfide 100 90 89.6Polydimethylsiloxane w/fumed silica — 10 10 Aminosilane — — 0.4Mechanical Properties Tensile elongation at break (%) 2.7 9.3 33.6Charpy Notched Impact Strength (23° C., 2.1 2.7 6.5 kJ/m²)

As can be seen, the addition of 10 wt. % of the ultrahigh molecularweight polydimethylsiloxane/fumed silica combination led to an increasein tensile elongation and break and a slight increase in impactstrength. The further addition of the coupling agent increased bothtensile elongation at break and impact strength.

Example 2

Materials utilized to form the compositions included the following:

Polyarylene sulfide:

PPS1—Fortron® 0203 polyphenylene sulfide available from TiconaEngineering Polymers of Florence, Ky.

PPS2—Fortron® 0205 polyphenylene sulfide available from TiconaEngineering Polymers of Florence, Ky.

PPS3—Fortron® 0214 polyphenylene sulfide available from TiconaEngineering Polymers of Florence, Ky.

Impact Modifier: LOTADER® AX8840—a random copolymer of ethylene andglycidyl methacrylate available from Arkema, Inc.

Crosslinking Agent: Terephthalic Acid

Lubricant: Glycolube® P available from Lonza Group Ltd.

Pigment: Black Concentrate

Filler: Fiber glass 910A-10C 4 mm, available from Owens Corning, Inc.

Samples were formed by blending the ingredients and melt extrudingthrough a WLE-25 mm at 310° C. followed by pelletizing. Sampleformulations (provided as weight percentage of the formulation) andtesting results are provided in the table below.

Samples 1 2 3 Components PPS1 — — 10.00 PPS2 — 81.20 71.20 PPS3 81.20 —— Lubricant 0.30 0.30 0.30 Impact Modifier 15.00 15.00 15.00Crosslinking agent 1.00 1.00 0.70 Pigment 2.50 2.50 2.50 Filler — — 5.00Mechanical Properties Tensile Modulus (MPa 50 mm/min) 2200 2300 3500Tensile Stress at Break (MPa) 51.1 55.6 77.8 Tensile Elongation at Break(%) 12.4 26.3 4.5 Charpy Notched Impact Strength 38.7 12.5 4.8 (23° C.,kJ/m²)

As can be seen, the combination of the polyarylene sulfide with theimpact modifier and the crosslinking agent can produce materials withhigh elongation at break and impact strength. The addition of 5 wt. %glass fiber increased the tensile modulus and the tensile stress atbreak.

Sample 2 was injection molded to form cable ties as illustrated in FIG.1 and FIG. 2. The cable ties were 0.5 inches wide by 15 inches long. Thecable ties were tested for loop strength retention during heat aging andchemical resistance. Results of the strength retention are shown in FIG.6 and chemical resistance results are shown in the table, below.

Fluid Sample 2 Engine oil ✓* Gasoline ✓ Gasohol ✓ Diesel Fuel ✓ PowerSteering Fluid ✓ Automatic Transmission Fluid ✓ Battery Acid ✓ BrakeFluid ✓ *No degradation or change in appearance observed after 72 hours

Heat aging of the cable ties was performed at 165° C. for 1000 hours.After 1000 hours, the cable ties had 71% retention in loop strength.

Chemical resistance was determined by performing the Fluids ResistanceTest specified in SAE J2192. Briefly, cable ties were immersed in eachtest fluid for 5 minutes, and then inspected for any signs ofdegradation over a 72 hour period. As shown in Table 2, no degradationwas observed in any of the test fluids.

These and other modifications and variations to the present disclosuremay be practiced by those of ordinary skill in the art, withoutdeparting from the spirit and scope of the present disclosure. Inaddition, it should be understood the aspects of the various embodimentsmay be interchanged, either in whole or in part. Furthermore, those ofordinary skill in the art will appreciate that the foregoing descriptionis by way of example only, and is not intended to limit the disclosure.

What is claimed is:
 1. An injection molded part having a thickness ofabout 100 millimeters or less, the injection molded part being formedfrom a thermoplastic composition that includes a polyarylene sulfide anda crosslinked impact modifier, the injection molded part exhibiting anotched Charpy impact strength of about 3 kJ/m² or greater as measuredaccording to ISO Test No. 179-1 at a temperature of 23° C., theinjection molded part exhibiting about 60% or more strength retentionfollowing heat aging at 165° C. for 1000 hours.
 2. The injection moldedpart of claim 1, wherein the injection molded part is a fastener.
 3. Theinjection molded part of claim 2, wherein the fastener is a cable tie, aclip, a band, a harness, a tape, a clamp, or a cable tie saddle.
 4. Theinjection molded part of claim 1, the injection molded part exhibiting anotched Charpy impact strength of about 8 kJ/m² or greater as measuredaccording to ISO Test No. 179-1 at a temperature of −30° C.
 5. Theinjection molded part of claim 1, wherein the injection molded partmeets the V-0 flammability standard at a thickness of 0.2 millimeters.6. The injection molded part of claim 1, wherein the injection moldedpart exhibits a flexural modulus of about 2500 MPa or less as determinedaccording to ISO Test No.
 178. 7. The injection molded part of claim 1,wherein the polyarylene sulfide is a polyphenylene sulfide.
 8. Theinjection molded part of claim 1, wherein the impact modifier is anolefinic terpolymer.
 9. The injection molded part of claim 1, whereinthe crosslinked impact modifier comprises the reaction product of anepoxy functionality of the impact modifier and a crosslinking agent orthe reaction product of maleic anhydride functionality of the impactmodifier and a crosslinked agent.
 10. The injection molded part of claim9, wherein the crosslinking agent is terephthalic acid.
 11. Theinjection molded part of claim 1, the thermoplastic composition furthercomprising a siloxane polymer.
 12. The injection molded part of claim11, wherein the siloxane polymer is a polydimethylsiloxane.
 13. Theinjection molded part of claim 12, wherein the polydimethylsiloxane isultrahigh molecular weight polydimethylsiloxane.
 14. The injectionmolded part of claim 11, the thermoplastic composition furthercomprising fumed silica.
 15. The injection molded part of claim 11, thethermoplastic composition further comprising a coupling agent.
 16. Theinjection molded part of claim 15, wherein the coupling agent is anamino silane coupling agent.
 17. The injection molded part of claim 1,the thermoplastic composition further comprising a thermoplasticelastomer.
 18. The injection molded part of claim 17, wherein thethermoplastic elastomer has a repeating structure represented by(A-B)_(n), wherein A is a hard segment and B is a soft segment.
 19. Theinjection molded part of claim 18, wherein the thermoplastic elastomercomprises alternating blocks of polyamide and polyether.
 20. Theinjection molded part of claim 1, the thermoplastic composition furthercomprising one or more additives.
 21. The injection molded part of claim20, wherein the one or more additives comprises one or more fillers. 22.The injection molded part of claim 21, wherein the one or more fillerscomprises fibrous fillers.
 23. A method for forming the injection moldedpart of claim 1, the method comprising: injecting the thermoplasticcomposition into a mold cavity, the thermoplastic composition having amelt viscosity of about 3 kilopoise or less as determined by a capillaryrheometer at a temperature of 310° C. and a shear rate of 1200seconds⁻¹; and ejecting the molded part from the mold cavity.